1 . Field of the Invention
The present invention relates to a seed supply mechanism for a seed coating/processing which automatically gathers seeds, from a large number of seeds accommodated within a seed vessel, to supply the gathered seeds to a gel extruding mechanism.
2. Description of the Prior Art
The seed supply mechanism is one of the units used in a seed coating/processing apparatus.
The seed coating/processing apparatus serves to coat seeds with a gel containing nutritive material and sanitizer for the seeds for protection, and also automatically successively carries out the seed coating/processing which gel-coats the seeds to make the coating of each seed spherical and to increase the diameter of the seed by gel-coating.
The seed supply mechanism in the seed coating/processing apparatus is provided over the gel extruding mechanism for producing a gel film. Incidentally, actually, sol of water solution containing mainly natrium alginate is extruded. When the concentration of the sol is increased, it serves as gel of calcium alginate.
The outline of the gel extruding mechanism will be explained below. As shown in FIG. 7, within a substantially rectangular parallelepiped valve body 1, a space 2 communicating with a gel pushing plunger (not shown) is formed. To an opening 3 of the lower end surface of the valve body 1, a pipe path (not shown) communicating with a gel reservoir is attached. Between the opening 3 and the space 2, a check valve whose opening 3 is opened/closed by a steel ball is formed. To the left side of the valve body, a valve case 5 is attached.
In the valve case 5, a flange 6a of a metallic nozzle plunger 8 is located at the lower end of a plunger insertion hole which vertically penetrates through the case 5; a bushing 7 is fit in the interior of the plunger insertion hole 6; and the nozzle plunger 8 which is hollow-cylindrical is inserted in the interior of the bushing 7 so that it can rise/fall.
The outer periphery of the nozzle plunger 8 forms a pressure receiving surface 8a at a lower half portion with a decreased diameter.
A gel flow path 9 which communicates the plunger insertion hole 6 with the space 2 is provided. The gel in the gel reservoir is supplied to the space 2 through the opening 3 and the check valve, and filled in the gel flow path 9 and the plunger insertion hole 6.
To the upper surface of the valve case 5, a cylindrical portion 10 surrounding the plunger insertion 6 is attached so that a female screw 11a provided in the interior of a spring adjuster 11 is screwed to a male screw 10a provided on the outer periphery of the cylindrical portion 10.
A spring receiver 12 is located on the nozzle plunger 8, and a spring 13 is inserted between the spring receiver 12 and the spring adjuster 11.
Thus, although the lower end of the nozzle plunger 8 forced downward closes its flange 6a, when the gel pushing plunger protrudes to boost the pressure of the gel, the pressure receiving surface 8a is pushed. As a result, the nozzle plunger 8 rises to open the valve so that the gel is extruded. When the gel pushing plunger retreats to lower the gel pressure, the nozzle plunger 8 lowers to open the valve and the gel is supplied from the check valve.
When the nozzle plunger 8 lowers to close the valve, the extrusion of the gel is stopped. The gel remaining on the lower surface of the valve sheet 6a forms the gel film coating the lower portion of the plunger insertion hole 6 by surface tension, and the gel film hangs down because of its own weight.
In synchronism with this, when seeds are dropped and supplied from a seed supply device provided above, gel-coated seeds are formed. These seeds drop together with the gel supplemented by next valve opening and supplied to a hardening reservoir while they form ball shapes because of surface tension.
The seed supply device is constituted as follows as disclosed in U.S. Pat. No. 5,254,358. To both ends of a rotating arm which rotates by 180.degree. by a rotary actuator, a hollow sucking nozzles each with its front end tapered is attached in such a manner that the tip is downward. The rear end is communicated with an air pressure source and a negative pressure source through an exchanging valve. A seed vessel is provided just below the sucking nozzle attached to the one end of the rotating arm and is provided so that it can rise and fall (otherwise, the sucking nozzle may be attached to the tip of the rod of an air cylinder for rise/fall). A gel extrusion mechanism is provided so that the nozzle plunger is located just below the sucking nozzle attached to the other end of the rotating arm.
The seed vessel rises to insert the tip of the sucking nozzle into a large number of seeds in the seed vessel. With the pressure in the sucking nozzle being negative, the seed(s) is thereinto. Thereafter, a rotating arm is rotated to release the negative pressure in the sucking nozzle (or to supply the air pressure into the sucking nozzle) so that the seed(s) is dropped and supplied into the gel film through the nozzle plunger 8.
The seed coating/processing apparatus described above has the following drawbacks.
By synchronously operating the seed supply device and gel extrusion mechanism, the coating/processing of seeds can be automatically carried out. But, there are several kinds of sizes and shapes of the seeds. Seeds having sharp tips such as lettuce and very minute seeds such as seeds of a celery flower are likely to be simultaneously sucked to the tip of the sucking nozzle when a sucking operation is once carried out. Thus, a redundant number of seeds are coated and processed together.